The present invention relates to a vehicle door latch device, and more particularly, to an anti-panic door latch device.
FIGS. 12 and 13 show a typical conventional vehicle door latch device. The conventional device comprises a latch A which is engageable with a striker B fixed to a vehicle body, a ratchet C which holds engagement of the latch A with the striker B by engaging with the latch A, a ratchet lever D which rotates with the ratchet C as one-piece, an open lever E which rotates from an initial position S to a door-opening position T in response to operation of a door-opening handle O of a vehicle door, a lock pin G which is slidably engaged with a slot F of the open lever E and moves in a given direction W by rotation of the open lever E, a lock lever H which is connected to a lock button P of the door and is displaceable between an unlocked position X and a locked position Y, an over-center spring J which holds the lock lever H by elasticity thereof at either the unlocked position X or the locked position Y with respect to a dead-center point Z thereof, and a connecting member K which connects the lock pin G and the lock lever H.
When displacing the lock lever H to the unlocked position X, the connecting member K moves the lock pin G within a concave portion L of the ratchet lever D, and when displacing the lock lever H to the locked position Y, the connecting member K moves the lock pin G outside the concave portion L.
A problem to be solved of the above prior art device is that when the opening handle O is operated to open the door in the locked state shown in FIG. 12, it becomes impossible to restore the lock lever H to the unlocked position X from the locked position Y. This state is often called a panic state of the door latch device. The panic state will be described in detail. In the locked state shown in FIG. 12, when the open lever E is displaced to the opening position T by the opening handle O, the lock pin G is shifted in the given direction W. However, at this moment, the door is not opened since the door is in the locked state. In this state where the open lever E is in the opening position T, when the lock button P is operated to unlock the latch device, the connecting member K is moved upward by counterclockwise rotation of the lock lever H, and the lock pin G is then brought into contact with a contact portion M of the ratchet lever D before the lock lever H goes over the dead-center point Z of the spring J. Thereby, further unlocking rotation of the lock lever H becomes impossible, and the door latch device remains locked. This state is a panic state of the door latch device.
In the above panic state, since the lock lever H is positioned between the locked position Y and the dead-center point Z, the lock lever H will be restored to the locked position Y by the elasticity of the over-center spring J when an operator releases his hold from the lock button P. In the prior art door latch device, when the panic state arises, it is necessary to move the lock button P in the unlocking direction again after restoring the open lever E to the initial position S, in order to unlock the door lath device.
U.S. Pat. No. 5,181,754 discloses another type of door latch device which also has the same problem. In this device, when an open lever (29) is rotated up to the door-opening position, a connecting member (33) is moved downward in FIG. 5 of the prior art, and an unnumbered bent portion adjacent to a lock pin (42) is engageably opposed to a contact portion (10) of a ratchet (6). In this state, when the lock button is operated to unlock the latch device, the connecting member (33, 39) is moved rightward by counterclockwise rotation of a lock lever (35), and the unnumbered bent portion is brought into contact with the contact portion (10) before the lock lever (35) goes over the dead-center point of a over-center spring. Thereby, unlocking of the prior art door latch device meets with failure.